tappoz / CalculatorIoData

A simple caluclator using Guice (dependency injection) and Mockito / PowerMock (unit testing) involving efficient I/O operations

CalculatorIoData

This Java project runs a list of operations e.g. add, divide, subtract, multiply according to a input file with instructions. The aim is to calculate a result from a set of instructions. The last instruction should be apply and a number (e.g., apply 3). The calculator is then initialised with that number and the previous instructions are applied to that number.

Basically the idea here is to skip all the lines in the file but the last to initialise the process. The I/O operations should be efficient, i.e. no loading of the whole file in memory before the computation.

• The Apache Commons frameworks help in this I/O scenario.
• Google Guice is used for the dependency injection pattern.
• For the Unit Tests Junit and Hamcrest are used. Also Mockito and PowerMock have been used when involving I/O operations with static methods.

Example

An input file example (containing 3 lines) might be:

add 2
multiply 3
apply 3

The system still works with negative numbers e.g. for the operation: add -3.

Compilation

Use Maven to compile it. Run the following command from the root folder of this project:

$ mvn clean package

Running the project

To run the project from a Linux command line, use the following command:

$ java -jar target/calculatorIo.jar src/main/resources/example3.txt

where:

• target/calculatorIo.jar is the path to the jar file;
• src/main/resources/example3.txt is the path to the input file with the instructions.